We're dividing 798438 by 21 
We want to figure out the number of times 798438 can be divided by 21.

On to step 1:
21 can be fit into 7 0 times, resulting in a remainder of 7.
The number 0 becomes the next digit in our result. 
Result so far: 0.0
If we subtract 0 from 7, we get 7.
Fetch the next digit (9) from the dividend, attach it to 7 and continue: 79 / 21

Advancing to step 2:
The number 21 fits into 79 3 times, leaving a remainder of 16.
The number 3 becomes the next digit in our result. 
Result so far: 3.0
Subtract 63 from 79 to get 16.
Take the next digit (8) from the dividend and append it to 16, then repeat: 168 / 21

Going ahead to step 3:
168 divided by 21 is 8 with a remainder of 0.
Write down 8 as next digit of the result. 
Result so far: 38.0
Subtract 168 from 168 to get 0.
Fetch the next digit (4) from the dividend, attach it to 0 and continue: 4 / 21

On to step 4:
21 can be fit into 4 0 times, resulting in a remainder of 4.
Put 0 as the next digit of the answer. 
Result so far: 380.0
Subtract 0 from 4 to get 4.
Grab the next digit (3) from the dividend, add it to 4, then carry on: 43 / 21

Moving on to step 5:
If we divide 43 by 21, we get 2 and a remainder of 1.
Record the quotient 2 as the next digit in the result. 
Result so far: 3802.0
If we take 42 away from 43, we end up with 1.
Take the next digit (8) from the dividend and append it to 1, then repeat: 18 / 21

Going ahead to step 6:
21 goes into 18 0 times with a remainder of 18.
Record the quotient 0 as the next digit in the result. 
Result so far: 38020.0
Deduct 0 from 18 and we're left with 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Advancing to step 7:
180 divided by 21 is 8 with a remainder of 12.
The next digit of our result is 8. 
Result so far: 38020.8
Subtract 168 from 180 to get 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

On to step 8:
120 divided by 21 is 5 with a remainder of 15.
Record the quotient 5 as the next digit in the result. 
Result so far: 38020.85
Deduct 105 from 120 and we're left with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

Moving on to step 9:
21 can be fit into 150 7 times, resulting in a remainder of 3.
Write down 7 as next digit of the result. 
Result so far: 38020.857
If we take 147 away from 150, we end up with 3.
Since there are no more digits in the dividend, we add a zero to the remainder making it 30, and continue the process.

On to step 10:
30 divided by 21 is 1 with a remainder of 9.
Record the quotient 1 as the next digit in the result. 
Result so far: 38020.8571
Subtracting 21 from 30 leaves us with 9.
Since there are no more digits in the dividend, we add a zero to the remainder making it 90, and continue the process.

Moving on to step 11:
If we divide 90 by 21, we get 4 and a remainder of 6.
Write down 4 as next digit of the result. 
Result so far: 38020.85714
If we take 84 away from 90, we end up with 6.
Since there are no more digits in the dividend, we add a zero to the remainder making it 60, and continue the process.

Going ahead to step 12:
21 can be fit into 60 2 times, resulting in a remainder of 18.
Write down 2 as next digit of the result. 
Result so far: 38020.857142
Subtract 42 from 60 to get 18.
Since there are no more digits in the dividend, we add a zero to the remainder making it 180, and continue the process.

Going ahead to step 13:
If we divide 180 by 21, we get 8 and a remainder of 12.
Write down 8 as next digit of the result. 
Result so far: 38020.8571428
Deduct 168 from 180 and we're left with 12.
Since there are no more digits in the dividend, we add a zero to the remainder making it 120, and continue the process.

Going ahead to step 14:
120 divided by 21 is 5 with a remainder of 15.
Put 5 as the next digit of the answer. 
Result so far: 38020.85714285
Subtracting 105 from 120 leaves us with 15.
Since there are no more digits in the dividend, we add a zero to the remainder making it 150, and continue the process.

The final outcome is 38020.85714285, with a leftover of 1.5e-08.